1. Field of the Invention
This invention generally relates to semiconductor memory devices, and, in particular, to regulating voltages in a memory, such as flash memory.
2. Description of the Related Art
Advancements in the memory technology have resulted in improved memories at a lower price. For example, flash memories today store a greater number of bits per area at an overall lower cost-per-megabyte. The affordable price of flash memory has made it a popular choice among many application developers.
Flash memory (sometimes called “flash RAM”) is a type of non-volatile memory that can be erased and reprogrammed in units of memory called blocks. Flash memory is a variation of electrically erasable programmable read-only memory (EEPROM) that, unlike flash memory, is erased and rewritten at the byte level, which is slower than flash memory updating. Flash memory is commonly used to hold control code such as the basic input/output system (BIOS) in a personal computer. When BIOS needs to be changed (rewritten), the flash memory can be written in block (rather than byte) sizes, making it faster to update. Applications employing flash memory include digital cellular phones, digital cameras, LAN switches, computers, digital set-up boxes, embedded controllers, and other devices.
Flash memories generally use factory programmed trim bits (sometimes also referred to as “option bits”) to configure the operation of the memory. The trim bits may be utilized to configure a variety of different settings in the memory, including voltage regulation levels and other marketing options. It may be desirable to regulate voltage levels in the memory during power up, for example, using voltage regulators, such as capacitor-divider voltage regulators. Furthermore, it may be desirable to have the new voltage take affect soon after the trim bits provide the new regulation voltage level. However, because selected voltage regulators, such as capacitor-divider voltage regulators, generally cannot change their voltage regulation value without a proper refresh of the capacitors, the new regulation value may not take effect as quickly as desired, thereby causing the regulators to operate unregulated.